Salt suitable for an acid generator and a chemically amplified resist composition containing the same

ABSTRACT

The present invention provides a salt of the formula (I):  
                 
 
wherein X represents alkylene group or substituted alkylene group; Q 1  and Q 2  each independently represent fluorine atom or perfluoroalkyl group having 1 to 6 carbon atoms; A +  represents organic counter ion; and n shows 0 or 1. 
The present invention also provides a chemically amplified resist composition comprising the salt of the formula (I), and a resin which contains a structural unit having an acid-labile group and which itself is insoluble or poorly soluble in an alkali aqueous solution but becomes soluble in an alkali aqueous solution by the action of an acid.

This nonprovisional application claims priority under 35 U.S.C. § 119(a)on Patent Application No. 2005-374256 filed in JAPAN on Dec. 27, 2005,the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a salt suitable for an acid generatorused for a chemically amplified resist composition which is used in fineprocessing of semiconductors, and a chemically amplified resistcomposition containing the salt

BACKGROUND OF THE INVENTION

A chemically amplified resist composition used for semiconductormicrofabrication employing a lithography process contains an acidgenerator comprising a compound generating an acid by irradiation.

In semiconductor microfabrication, it is desirable to form patternshaving high resolution, and it is expected for a chemically amplifiedresist composition to give such patterns.

Recently, a chemically amplified resist composition containingtriphenylsulfonium 1-adamantanemethoxycarbonyldifluoromethansulfonate,p-tolyldiphenylsulfonium perfluorooctanesulfonate, and the like areproposed (e.g. JP2004-4561-A), and a salt providing a chemicallyamplified resist composition giving patterns having higher resolution.

SUMMARY OF THE INVENTION

Objects of the present invention are to provide a salt suitable for anacid generator capable of providing chemically amplified resistcompositions giving patterns having better resolution and a process forproducing the salt.

Another objects of the present invention are to provide syntheticintermediates for the salts and to provide a process for producing thesynthetic intermediates or the salts.

Still another object of the present invention are to provide achemically amplified resist composition containing the salts.

These and other objects of the present invention will be apparent fromthe following description.

The present invention relates to the followings:

-   <1> A salt of the formula (I):    wherein X represents alkylene group or substituted alkylene group in    which a —CH₂— except for the one connected to the adjacent —COO— is    substituted with —S—or —O—; Y represents hydrocarbon ring group    containing at least one aromatic ring and having 5 to 30 carbon    atoms in which one or more of —CH₂— on the hydrocarbon ring is    optionally substituted with —O— or —CO— and in which one or more of    hydrogen atom on the hydrocarbon ring is optionally substituted with    alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6    carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms,    hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group or    cyano group; Q¹ and Q² each independently represent fluorine atom or    perfluoroalkyl group having 1 to 6 carbon atoms; A⁺ represents    organic counter ion; and n shows 0 or 1. Hereinafter, the salt of    the formula (I) may also be referred to as Salt (I).-   <2> The salt according to <1>, wherein each of Q¹ and Q² is fluorine    atom or trifluoromethyl group.-   <3> The salt according to <1> or <2>, wherein n is 1 and X is    alkylene group having 1 to 6 carbon atoms or substituted alkylene    group having 1 to 6 carbon atoms in which a —CH₂— except for the one    connected to the adjacent —COO— is substituted with —S—or —O.-   <4> The salt according to <1> or <2>, wherein n is 0.-   <5> The salt according to any of <1> to <3>, wherein X is —CH₂—,    —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂— or —CH₂CH₂—O—.-   <6> The salt according to any of <1> to <5>, wherein Y is aromatic    ring group having 5 to 20 carbon atoms in which one or more of    hydrogen atom in the aromatic ring is optionally substituted with    alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6    carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms,    hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group or    cyano group.-   <7> The salt according to any of <1> to <5>, wherein Y is phenyl    group, naphthyl group, anthryl group, phenanthryl group or fluorenyl    group in which one or more of hydrogen atom on the ring is    optionally substituted with alkyl group having 1 to 6 carbon atoms,    alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having    1 to 4 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms,    hydroxyl group or cyano group.-   <8> The salt according to any of <1> to <7>, wherein A⁺ is at least    one cation selected from the group consisting of the formula (IIe),    the formula (IIb), the formula (IIc) and the formula (IId):-   a cation of the formula (IIe);-    wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl group    having 1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to    30 carbon atoms, wherein one or more hydrogen atom in the alkyl    group is optionally substituted with hydroxyl group, alkoxy group    having 1 to 12 carbon atoms or cyclic hydrocarbon group having 3 to    12 carbon atoms and wherein one or more hydrogen atom in the cyclic    hydrocarbon group is optionally substituted with hydroxyl group,    alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to    12 carbon atoms,-   a cation of the formula (IIb);-    wherein P⁴ and P⁵ each independently represent hydrogen atom,    hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy    group having 1 to 12 carbon atoms;-   a cation of the formula (IIc);-    wherein P⁶ and P⁷ each independently represent alkyl having 1 to 12    carbon atoms or cycloalkyl having 3 to 12 carbon atoms, or P⁶ and P⁷    bond to form divalent acyclic hydrocarbon group having 3 to 12    carbon atoms which forms a ring together with the adjacent S⁺, and    at least one —CH₂— in the divalent acyclic hydrocarbon group is    optionally substituted by —CO—, —O— or —S—, P⁸ represents hydrogen,    P⁹ represents alkyl having 1 to 12 carbon atoms, cycloalkyl having 3    to 12 carbon atoms or aromatic ring group optionally substituted, or    P⁸ and P⁹ bond to form divalent acyclic hydrocarbon group which    forms 2-oxocycloalkyl together with the adjacent —CHCO—, and at    least one —CH₂— in the divalent acyclic hydrocarbon group is    optionally substituted by —CO—, —O— or —S—; and-   a cation of the formula (IId);-    wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and    P²¹ each independently represent hydrogen atom, hydroxyl group,    alkyl group having 1 to 12 carbon atoms or alkoxy group having 1 to    12 carbon atoms, B represents sulfur atom or oxygen atom, and m    represents 0 or 1.-   <9> The salt according to <8>, wherein the cation of the formula    (IIe) is a cation of the formula (IIf), (IIg) or (IIh):-    wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group    having 1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to    30 except phenyl group, wherein one or more hydrogen atom in the    alkyl group is optionally substituted with hydroxyl group, alkoxy    group having 1 to 12 carbon atoms or cyclic hydrocarbon group having    3 to 12 carbon atoms and wherein one or more hydrogen atom in the    cyclic hydrocarbon group is optionally substituted with hydroxyl    group, alkyl group having 1 to 12 carbon atoms or alkoxy group    having 1 to 12 carbon atoms; and P³¹, P³² P³³, P³⁴, P³⁵ and P³⁶ each    independently represent hydroxyl group, alkyl group having 1 to 12    carbon atoms, alkoxy group having 1 to 12 carbon atoms or cyclic    hydrocarbon group having 3 to 12 carbon atoms, and l, k, j, i, h and    g each independently show an integer of 0 to 5.-   <10> The salt according to <8>, wherein the cation of the formula    (IIe) is a cation of the formula (IIa):-    wherein P¹, P² and P³ each independently represent hydrogen atom,    hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy    group having 1 to 12 carbon atoms.-   <11> The salt according to <10>, wherein the cation of the formula    (IIa) is a cation of the formula (IIi):-    wherein P²², P²³ and P²⁴ each independently represent hydrogen atom    or alkyl group having 1 to 4 atoms.-   <12> The salt according to any of <1> to <8>, wherein the salt is    that of the formula (IIIa), (IIIb), (IIIc), (IIId) or (IIIe):-    wherein n1 shows an integer of 0 to 6, n2 shows an integer of 1 to    6, and P²², P²³ and P²⁴ have the same meanings as defined above.-   <13> A salt of the formula (IV):-    wherein M represents Li, Na, K or Ag, and X, Y, Q¹, Q² and n have    the same meanings as defined above.-   <14> A process for producing a salt of the formula (IV)-   which comprises esterifying an alcohol of the formula (V):    HO—(X)_(n)—Y  (V)-    wherein X, Y and n have the same meanings as defined above, with a    carboxylic acid of the formula (VI):-    wherein M and Q have the same meanings as defined above.-   <15> A process for producing Salt (I):-   which comprises reacting a salt of the formula (IV) with a compound    of the formula (VII):    A⁺Z⁻  (VII)-    wherein Z represents F, Cl, Br, I, BF₄, AsF₆, SbF₆, PF₆ or ClO₄,    and A⁺ has the same meaning as defined above.-   <16> A chemically amplified resist composition comprising Salt (I),    and a resin which contains a structural unit having an acid-labile    group and which itself is insoluble or poorly soluble in an alkali    aqueous solution but becomes soluble in an alkali aqueous solution    by the action of an acid.-   <17> The composition according to <16>, wherein each of Q¹ and Q² is    fluorine atom or trifluoromethyl group.-   <18> The composition according to <16> or <17>, wherein the resin    contains a structural unit derived from a monomer having a bulky and    acid-labile group.-   <19> The composition according to <18>, wherein the bulky and    acid-labile group is 2-alkyl-2-adamantyl group or    1-(1-adamantyl)-1-alkylalkyl group.-   <20> The composition according to <18>, wherein the monomer having    bulky and acid-labile group is 2-alkyl-2-adamantyl (meth)acrylate,    1-(1-adamantyl)-1-alkylalkyl (meth)acrylate, 2-alkyl-2-adamantyl    5-norbornene-2-carboxylate, 1-(1-adamantyl)-1-alkylalkyl    5-norbornene-2-Carboxylate, 2-alkyl-2-adamantyl α-chloroacrylate or    1-(1-adamantyl)-1-alkylalkyl α-chloroacrylate.-   <21> The composition according to any of <16> to <20>, wherein the    composition further comprises a basic compound.-   <22> The composition according to any of <16> to <21>, wherein n is    1 and X is alkylene group having 1 to 6 carbon atoms or substituted    alkylene group having 1 to 6 carbon atoms in which a —CH₂— except    for the one connected to the adjacent —COO— is substituted with    —S—or —O—.-   <23> The composition according to any of <16> to <21>, wherein n is    0.-   <24> The composition according to any of <16> to <22>, wherein X is    —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂— or —CH₂CH₂—O—.-   <25> The composition according to any of <16> to <24>, wherein Y is    aromatic ring group having 5 to 20 carbon atoms in which one or more    of hydrogen atom on the aromatic ring is optionally substituted with    alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6    carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms,    hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group or    cyano group.-   <26> The composition according to any of <16> to <25>, wherein Y is    phenyl group, naphthyl group, anthryl group, phenanthryl group or    fluorenyl group in which one or more of hydrogen atom on the ring is    optionally substituted with alkyl group having 1 to 6 carbon atoms,    alkoxy group having 1 to 6 carbon atoms, perfluoroalkyl group having    1 to 4 carbon atoms, hydroxyalkyl group having 1 to 6 carbon atoms,    hydroxyl group or cyano group.-   <27> The composition according to any of <16> to <26>, wherein A⁺ is    at least one cation selected from the group consisting of the    formula (IIe), the formula (IIb), the formula (IIc) and the formula    (IId).-   <28> The composition according to <27>, wherein the cation of the    formula (IIe) is a cation of the formula (IIf), (IIg) or (IIh).-   <29> The composition according to <27>, wherein the cation of the    formula (IIe) is a cation of the formula (IIa).-   <30> The composition according to <29>, wherein the cation of the    formula (IIa) is a cation of the formula (IIi).-   <31> The composition according to any of <16> to <27>, wherein the    salt is that of the formula (IIIa), (IIIb), (IIIc), (IIId) or    (IIIe).

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention provides Salt (I).

The X in the formulae (I), (IV) and (V) represents alkylene group orsubstituted alkylene group in which a —CH₂— is substituted with —S—or—O—. However, the —CH₂— connected to the adjacent —COO— may not besubstituted. The alkylene group or the substituted alkylene groupusually has 1 to 6 carbon atoms. Examples of X include —CH₂—, —CH₂CH₂—,—CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂ CH₂CH₂—,—CH₂—O—, —CH₂—O—CH₂—, —CH₂CH₂—O—, —CH₂—O—CH₂CH₂—, —CH₂CH₂—O—CH₂—,—CH₂CH₂CH₂—O—, —CH₂—O—CH₂CH₂CH₂—, —CH₂CH₂—O—CH₂CH₂—, —CH₂CH₂CH₂—O—CH₂—,—CH₂CH₂CH₂CH₂—O—, —CH₂—O—CH₂CH₂CH₂CH₂—, —CH₂CH₂—O—CH₂CH₂CH₂CH₂—,—CH₂CH₂CH₂—O—CH₂CH₂—, —CH₂CH₂CH₂CH₂—O—CH₂—, —CH₂—S—, —CH₂—S—CH₂—,—CH₂—O—CH₂CH₂—O—CH₂—, —CH₂CH₂—O—CH₂CH₂—O—, —CH₂—CH₂CH₂—S—,—CH₂—S—CH₂CH₂—, —CH₂CH₂—S—CH₂—, —CH₂—S—CH₂CH₂CH₂—, —CH₂CH₂—S—CH₂CH₂—,—CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂—S—, —CH₂—S—CH₂CH₂CH₂CH₂—,—CH₂CH₂—S—CH₂CH₂CH₂—, —CH₂CH₂CH₂—S—CH₂CH₂—, —CH₂CH₂CH₂CH₂—S—CH₂—,—CH₂—S—CH₂CH₂—S—CH₂——CH₂CH₂CH₂CH₂CH₂—S— and —CH₂CH₂—S—CH₂CH₂—S—, and—CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂— and —CH₂CH₂—O— arepreferred.

Y can directly be connected to the —COO— in the formulae (I) and (IV) orto the OH in the formula (V) without X, which is the case that n shows0.

Y in the formulae (I), (IV) and (V) represents hydrocarbon ring groupcontaining at least one aromatic ring and having 5 to 30 carbon atoms.One or more of —CH₂— on the hydrocarbon ring group is optionallysubstituted with —O— or —CO—. One or more of hydrogen atom on thehydrocarbon ring group is optionally substituted with alkyl group having1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group. Examples ofthe aromatic ring include benzene ring, naphthalene ring, anthracenering and phenanthrene ring. Y may be aromatic ring group having 5 to 30carbon atoms, in which one or more of —CH₂— on the aromatic ring isoptionally substituted with —O— or —CO— and in which one or more ofhydrogen atom in the aromatic ring is optionally substituted with alkylgroup having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbonatoms, perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkylgroup having 1 to 6 carbon atoms, hydroxyl group or cyano group.

Examples of Y include phenyl group, naphthyl group, anthryl group,phenanthryl group or fluorenyl group in which one or more of hydrogenatom on the ring is optionally substituted with alkyl group having 1 to6 carbon atoms, alkoxy group having 1 to 6 carbon atoms, perfluoroalkylgroup having 1 to 4 carbon atoms, hydroxyalkyl group having 1 to 6carbon atoms, hydroxyl group or cyano group. Specific examples thereofinclude phenyl group, 1-naphthyl group, 2-naphthyl group,5-hydroxy-1-naphthyl group, 5-hydroxy-2-naphthyl group, 1-anthryl group,2-anthryl group, 9-anthryl group, 3-phenanthryl group, 4-phenanthrylgroup, 9-phenanthryl group, 5-phenalenyl group, 9-fluorenyl group and1-anthraquinonyl group.

Q¹ and Q² each independently represent fluorine atom or perfluoroalkylgroup having 1 to 6 carbon atoms such as trifluoromethyl group,pentafluoroethyl group, heptafluoropropyl group, nonafluorobutyl group,and the like. As Q¹ and Q², fluorine atom and trifluoromethyl group arepreferred.

Specific examples of anion part of the Salt (I) include the following:

A⁺ in the formulae (I) and (VII) represents organic counter ion.Examples thereof include the cations of the formulae (IIe), (IIb), (IIc)and (IId).

In the cation of the formula (IIe), P²⁵, P²⁶ and P²⁷ each independentlyrepresent alkyl group having 1 to 30 carbon atoms or cyclic hydrocarbongroup having 3 to 30 carbon atoms. One or more hydrogen atom in thealkyl group in the formula (IIe) is optionally substituted with hydroxylgroup, alkoxy group having 1 to 12 carbon atoms or cyclic hydrocarbongroup having 3 to 12 carbon atoms and one or more hydrogen atom in thecyclic hydrocarbon group in the formula (IIe) is optionally substitutedwith hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxygroup having 1 to 12 carbon atoms.

Examples of the alkyl group in the formula (IIe) include methyl group,ethyl group, propyl group, isopropyl group, n-butyl group, sec-butylgroup, tert-butyl group, pentyl group, hexyl group, octyl group,2-ethylhexyl group, and the like, and examples of the alkoxy groupinclude methoxy group, ethoxy group, propoxy group, butoxy group,hexyloxy group, octyloxy group, 2-ethylhexyloxy group, and the like.Examples of the cyclic hydrocarbon group include cyclopentyl group,cyclohexyl group, adamantyl group, bicyclohexyl group, phenyl group,naphthyl group, fluorenyl group, biphenyl group, and the like.

In the cation of the formula (IIe), cations of the formulae (IIf), (IIg)and (IIh) are preferred. In the cations of the formulae (IIf), (IIg) and(IIh), P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group. One or more hydrogen atom in the alkyl group in theformulae (IIf), (IIg) and (IIh) is optionally substituted with hydroxylgroup, alkoxy group having 1 to 12 carbon atoms or cyclic hydrocarbongroup having 3 to 12 carbon atoms. One or more hydrogen atom in thecyclic hydrocarbon group in the formulae (IIf), (IIg) and (IIh) isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms. Examples ofthe alkyl group, alkoxy group and cyclic hydrocarbon group include thesame groups as mentioned in the formula (IIe) above.

P³¹, P³², P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydroxylgroup, alkyl group having 1 to 12 carbon atoms, alkoxy group having 1 to12 carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms,and l, k, j, i, h and g each independently show an integer of 0 to 5.Examples of the alkyl group, alkoxy group and cyclic hydrocarbon groupinclude the same groups as mentioned in the formula (IIe) above.

In the cation of the formula (IIe), the one of the formula (IIa) is morepreferred. In the cation of the formula (IIa), P¹, P² and P³ eachindependently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms.

Examples of the alkyl group and alkoxy group in the formula (IIa)include the same groups as mentioned in the formula (IIe) above.

In the cation of the formula (IIa), the one of the formula (IIi) aboveis preferred for the easiness of production.

In the cation of the formula (IIb), P⁴ and P⁵ each independentlyrepresent hydrogen atom, hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms. Examples ofthe alkyl group and alkoxy group include the same groups as mentioned inthe formula (IIe) above.

In the cation of the formula (IIc), P⁶ and P⁷ each independentlyrepresent alkyl having 1 to 12 carbon atoms or cycloalkyl having 3 to 12carbon atoms, or P⁶ and P⁷ bond to form divalent acyclic hydrocarbongroup having 3 to 12 carbon atoms which forms a ring together with theadjacent S⁺, and at least one —CH₂— in the divalent acyclic hydrocarbonmay be substituted with —CO—, —O— or —S—.

P⁸ represents hydrogen, P⁹ represents alkyl having 1 to 12 carbon atoms,cycloalkyl having 3 to 12 carbon atoms or aromatic ring group optionallysubstituted, or P⁸ and P⁹ bond to form divalent acyclic hydrocarbongroup which forms 2-oxocycloalkyl together with the adjacent —CHCO—, andone or more —CH₂— in the divalent acyclic hydrocarbon group isoptionally substituted with —CO—, —O— or —S—.

In P⁶, P⁷ and P⁹, specific examples of the alkyl group include methylgroup, ethyl group, propyl group, isopropyl group, butyl group,tert-butyl group, pentyl group, hexyl group, and the like, and specificexamples of the cycloalkyl group include cyclopropyl group, cyclobutylgroup, cyclopentyl group, cyclohexyl group, cycloheptyl group,cyclodecyl group, and the like. Specific examples of the divalentacyclic hydrocarbon group having 3 to 12 carbon atoms formed by bondingP⁶ and P⁷ include trimethylene group, tetramethylene group,pentamethylene group, and the like, and specific examples of the ringgroup formed by adjacent S⁺ and divalent acyclic hydrocarbon group by P⁶and P⁷ include pentamethylenesulfonio group, tetramethylenesulfoniogroup, oxybisethylenesulfonio group, and the like. In P⁹, specificexamples of the aromatic ring group include phenyl, tolyl, xylyl,naphthyl and the like. Specific examples of the divalent acyclichydrocarbon group formed by bonding P⁸ and P⁹ include methylene group,ethylene group, trimethylene group, tetramethylene group, pentamethylenegroup, and the like, and specific examples of the 2-oxocycloalkyl formedby bonding P⁸ and P⁹ together with the adjacent —CHCO— include2-oxocyclohexyl, 2-oxocyclopentyl and the like.

In the cation of the formula (IId), P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶,P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms, B represents sulfur atom or oxygen atom,and m represents 0 or 1. Examples of the alkyl group and alkoxy groupinclude the same groups as mentioned in the formula (IIe) above.

As A⁺, at least one cation selected from the group consisting of thecations of the formulae (IIf), (IIg), (IIh), (IIb), (IIc) and (IId) ispreferred, and at least one cation selected from the group consisting ofthe cations of the formulae (IIa), (IIb), (IIc) and (IId) is alsopreferred. As A⁺, the cation of the formula (IIi) is more preferred.

Specific examples of the cation of the formula (IIe) include thefollowing:

Specific examples of the formula (IIb) include the following:

Specific examples of the formula (IIc) include the following:

Specific examples of the cation of the formula (IId) include thefollowing:

As Salt (I), the salt of the formulae (IIIa), (IIIb), (IIIc), (IIId) and(IIIe) are preferred for providing chemically amplified resistcompositions giving patterns having higher resolution.

Examples of a process for production of Salt (I) include a processcomprising reacting a salt of the formula (IV) with the compound of theformula (VII), in an inert solvent such as acetonitrile, water,methanol, chloroform and dichloromethane at a temperature of 0 to 150°C., preferably of 0 to 100° C.

The amount of the compound of the formula (VII) is usually 0.5 to 2 molper 1 mol of the salt of the formula (IV). Salt (I) obtained can betaken out by recrystallization when it is in crystal form or byextraction by solvents and concentration when it is in oil form.

Examples of a process for production of the salt of the formula (IV)include a process reacting an alcohol of the formula (V) with acarboxylic acid of the formula (VI).

The esterification reaction can generally be carried out by mixingmaterials in an aprotic solvent such as dichloroethane, toluene,ethylbenzene, monochlorobenzene, acetonitrile, N,N-dimethylformamide,and the like, at 20 to 200° C., preferably 50 to 150° C. In theesterification reaction, an acid catalyst or a dehydrating agent isusually added, and examples of the acid catalyst include organic acidssuch as p-toluenesulfonic acid, inorganic acids such as sulfuric acid,and the like. Examples of the dehydrating agent include1,1-carbonyldiimidazole, N,N′-dicyclohexylcarbodiimide, and the like.

The esterification may preferably be carried out with dehydration, forexample, by Dean and Stark method as the reaction time tends to beshortened.

The amount of the carboxylic acid of the formula (VI) is usually 0.2 to3 mol, preferably 0.5 to 2 mol per 1 mol of the alcohol of the formula(V). The amount of the acid catalyst may be catalytic amount or theamount equivalent to solvent, and is usually 0.001 to 5 mol per 1 mol ofthe alcohol of the formula (V). The amount of the dehydrating agent isusually 0.2 to 5 mol, preferably 0.5 to 3 mol per 1 mol of the alcoholof the formula (V).

The present chemically amplified resist composition comprises Salt (I)and a resin which contains a structural unit having an acid-labile groupand which itself is insoluble or poorly soluble in an alkali aqueoussolution but becomes soluble in an alkali aqueous solution by the actionof an acid.

Salt (I) is usually used as an acid generator, and the acid generated byirradiation to Salt (I) catalytically acts against acid-labile groups ina resin, cleaves the acid-labile-group, and the resin becomes soluble inan alkali aqueous solution. Such a composition is suitable forchemically amplified positive resist composition.

The resin used for the present composition contains a structural unithaving an acid-labile group and which itself is insoluble or poorlysoluble in an alkali aqueous solution, but acid-labile group cleave byan acid. The resin after the cleavage contains carboxylic acid residueand as a result, the resin becomes soluble in an alkali aqueoussolution.

In the present specification, “—COOR” may be described as “a structurehaving ester of carboxylic acid”, and may also be abbreviated as “estergroup”. Specifically, “—COOC(CH₃)₃” may be described as “a structurehaving tert-butyl ester of carboxylic acid”, or be abbreviated as“tert-butyl ester group”.

Examples of the acid-labile group include a structure having ester ofcarboxylic acid such as alkyl ester group in which a carbon atomadjacent to the oxygen atom is quaternary carbon atom, and alicyclicester group in which a carbon atom adjacent to the oxygen atom isquaternary carbon atom, and the like, a lactone ring group in which acarbon atom adjacent to the oxygen atom is quaternary carbon atom, andthe like.

The “quaternary carbon atom” means a “carbon atom joined to foursubstituents other than hydrogen atom”.

Examples of the acid-labile group include alkyl ester group in which acarbon atom adjacent to the oxygen atom is quaternary carbon atom suchas tert-butyl ester group; acetal type ester group such as methoxymethylester group, ethoxymethyl ester group, 1-ethoxyethyl ester group,1-isobutoxyethyl ester group, 1-isopropoxyethyl ester group,1-ethoxypropoxy ester group, 1-(2-methoxyethoxy)ethyl ester,1-(2-acetoxyethoxy)ethyl ester group, 1-[2-(1-adamantyloxy)ethoxy]ethylester group, 1-[2-(1-adamantanecarbonyloxy)ethoxy]ethyl ester group,tetrahydro-2-furyl ester and tetrahydro-2-pyranyl ester group; alicyclicester group in which a carbon atom adjacent to the oxygen atom isquaternary carbon atom, such as isobornyl ester group, 1-alkylcycloalkylester group, 2-alkyl-2-adamantyl ester group,1-(1-adamantyl)-1-alkylalkyl ester group, and the like.

Examples of structures including the ester group include ester of(meth)acrylic acid structure, ester of norbornenecarboxylic acidstructure, ester of tricyclodecenecarboxylic acid structure,tetracyclodecenecarboxylic acid structure, and the like. At least onehydrogen atom in the adamantyl group above may be substituted byhydroxyl group.

The resin used for the present composition can be obtained by additionpolymerization of monomer(s) having an acid-labile group and olefinicdouble bond.

Among the monomers, it is preferable to use those having a bulky groupsuch as alicyclic group (e.g. 2-alkyl-2-adamantyl and1-(1-adamantyl)-1-alkylalkyl), as the group dissociated by the action ofan acid, since excellent resolution is obtained when used in the presentcomposition.

Examples of such monomer containing a bulky group include2-alkyl-2-adamantyl (meth)acrylate, 1-(1-adamantyl)-1-alkylalkyl(meth)acrylate, 2-alkyl-2-adamantyl 5-norbomene-2-carboxylate,1-(1-adamantyl)-1-alkylalkyl 5-norbornene-2-carboxylate,2-alkyl-2-adamantyl α-chloroacrylate, 1-(1-adamantyl)-1-alkylalkylα-chloroacrylate and the like.

Particularly when 2-alkyl-2-adamantyl (meth)acrylate or2-alkyl-2-adamantyl α-chloroacrylate is used as the monomer for theresin component in the present composition, resist composition havingexcellent resolution tend to be obtained. Typical examples of such2-alkyl-2-adamantyl (meth)acrylate and 2-alkyl-2-adamantylα-chloroacrylate include 2-methyl-2-adamantyl acrylate,2-methyl-2-adamantyl methacrylate, 2-ethyl-2-adamantyl acrylate,2-ethyl-2-adamantyl methacrylate, 2-n-butyl-2-adamantyl acrylate,2-methyl-2-adamantyl α-chloroacrylate, 2-ethyl-2-adamantylα-chloroacrylate and the like. When particularly 2-ethyl-2-adamantyl(meth)acrylate or 2-isopropyl-2-adamantyl (meth)acrylate is used for thepresent composition, composition having excellent sensitivity and heatresistance tends to be obtained. In the present invention, two or morekind of monomers having group dissociated by the action of an acid maybe used together, if necessary.

2-Alkyl-2-adamantyl (meth)acrylate can usually be produced by reacting2-alkyl-2-adamantanol or metal salt thereof with an acrylic halide ormethacrylic halide.

The resin used for the present composition can also contain, in additionto the above-mentioned structural units having an acid-labile group,other structural unit derived from acid-stable monomer. Herein, the“structural unit derived from acid-stable monomer” means “a structuralunit not dissociated by an acid generated from Salt (I)”.

Examples of such other structural units which can be contained includestructural units derived from monomers having a free carboxyl group suchas acrylic acid and methacrylic acid, structural units derived fromaliphatic unsaturated dicarboxylic anhydrides such as maleic anhydrideand itaconic anhydride, structural units derived from 2-norbomene,structural units derived from (meth)acrylonitrile, structural unitsderived from alkyl (meth)acrylate in which a carbon atom adjacent tooxygen atom is secondary or tertiary carbon atom, structural unitsderived from 1-adamantyl (meth)acrylate, structural units derived fromstyrenes such as p- or m-hydroxystyrene, structural units derived from(meth)acryloyloxy-y-butyrolactone having a lactone ring optionallysubstituted by alkyl, and the like. Herein, 1-adamantyl ester group is aacid-stable group though the carbon atom adjacent to oxygen atom is aquaternary carbon atom, and at least one hydrogen atom on 1-adamantyester group may be substituted by hydroxy group.

Specific examples of structural unit derived from acid-stable monomerinclude a structural unit derived from 3-hydroxyl-1-adamantyl(meth)acrylate, a structural unit derived from 3,5-dihydroxy-1-adamantyl(meth)acrylate, a structural unit derived fromα-(meth)acryloyloxy-y-butyrolactone, a structural unit derived fromβ-(meth)acryloyloxy-y-butyrolactone, a structural unit of the followingformula (a), a structural unit derived from the following formula (b), astructural unit derived from alicyclic compound having olefinic doublebond such as a structural unit of the following formula (c), astructural unit derived from aliphatic unsaturated dicarboxylicanhydride such as a structural unit of the formula (d), a structuralunit of the formula (e), and the like.

Particularly, to contain, in addition to the structural unit having anacid-labile group, further at least one structural unit selected fromthe group consisting of a structural unit derived from p-hydroxystyrene,a structural unit derived from m-hydroxystyrene, a structural unitderived from 3-hydroxy-1-adamantyl (meth)acrylate, a structural unitderived from 3,5-dihydroxy-1-adamantyl (meth)acrylate, a structural unitof the following formula (a) and a structural unit of the followingformula (b), in the resin in the present composition, is preferable fromthe standpoint of the adhesiveness of resist to a substrate andresolution of resist.

In the formulae (a) and (b), R¹ and R² each independently representhydrogen atom, methyl group or trifluoromethyl group and R³ and R⁴ eachindependently represent methyl group, trifluoromethyl group or halogenatom, and p and q each independently represent an integer of 0 to 3.When p represents 2 or 3, each of the R³ may be the same or differentand when q represents 2 or 3, each of the R⁴ may be the same ordifferent.

3-Hydroxy-1-adamantyl (meth)acrylate and 3,5-dihydroxy-1-adamantyl(meth)acrylate can be produced, for example, by reacting correspondinghydroxyadamantane with (meth)acrylic acid or its acid halide, and theyare also commercially available.

Further, (meth)acryloyloxy-y-butyrolactone having a lactone ringoptionally substituted by alkyl can be produced by reactingcorresponding α- or β-bromo-γ-butyrolactone with acrylic acid ormethacrylic acid, or reacting corresponding α- orβ-hydroxy-γ-butyrolactone with acrylic halide or methacrylic halide.

As monomers to give structural units of the formulae (a) and (b),specifically listed are, for example, (meth)acrylates of alicycliclactones having hydroxyl described below, and mixtures thereof, and thelike. These esters can be produced, for example, by reactingcorresponding alicyclic lactone having hydroxyl with (meth)acrylicacids, and the production method thereof is described in, for example,JP2000-26446-A.

Examples of the (meth)acryloyloxy-γ-butyrolactone having a lactone ringoptionally substituted by alkyl include α-acryloyloxy-γ-butyrolactone,α-methacryloyloxy-γ-butyrolactone,α-acryloyloxy-β,β-dimethyl-γ-butyrolactone,α-methacryloyloxy-β,β-dimethyl-γ-butyrolactone,α-acryloyloxy-α-methyl-γ-butyrolactone,α-methacryloyloxy-α-methyl-γ-butyrolactone,β-acryloyloxy-γ-butyrolactone, β-methacryloyloxy-γ-butyrolactone,β-methacryloyloxy-α-methyl-γ-butyrolactone and the like.

In the case of KrF lithography, even in the case of using a structureunit derived from hydroxystyrene such as p- and m-hydroxystyrene, as oneof the resin components, resist composition having sufficienttransparency can be obtained. For obtaining such copolymerizationresins, the corresponding (meth)acrylic ester monomer can beradical-polymerized with acetoxystyrene and styrene, and then theacetoxy group in the structure unit derived from acetoxystyrene can bede-acetylated with an acid.

The resin containing a structural unit derived from 2-norbomene showsstrong structure because alicyclic group is directly present on its mainchain and shows a property that dry etching resistance is excellent. Thestructural unit derived from 2-norbomene can be introduced into the mainchain by radical polymerization using, for example, in addition tocorresponding 2-norbomene, aliphatic unsaturated dicarboxylic anhydridessuch as maleic anhydride and itaconic anhydride together. The structuralunit derived from 2-norbornene is formed by opening of its double bond,and can be represented by the formula (c). The structural unit derivedfrom maleic anhydride and the structural unit derived from itaconicanhydride which are the structural unit derived from aliphaticunsaturated dicarboxylic anhydrides are formed by opening of theirdouble bonds, and can be represented by the formula (d) and the formula(e), respectively.

Here, R⁵ and R⁶ in the formula (c) each independently representhydrogen, alkyl having 1 to 3 carbon atoms, hydroxyalkyl having 1 to 3carbon atoms, carboxyl, cyano or —COOU group in which U representsalcohol residue, or R⁵ and R⁶ can bond together to form a carboxylicanhydride residue represented. by —C(═O)OC(═O)—.

In R⁵ and R⁶, examples of the alkyl include methyl, ethyl, propyl andisopropyl, specific examples of hydroxyalkyl include hydroxymethyl,2-hydroxyethyl and the like.

In R⁵ and R⁶, —COOU group is an ester formed from carboxyl, and as thealcohol residue corresponding to U, for example, optionally substitutedalkyls having about 1 to 8 carbon atoms, 2-oxooxolan-3- or -4-yl and thelike are listed, and as the substituent on the alkyl, hydroxyl,alicyclic hydrocarbon residues and the like are listed.

Specific examples of the monomer used to give the structural unitrepresented by the formula (c) may include the followings;

2-norbornene,

2-hydroxy-5-norbomene,

5-norbornen-2-carboxylic acid,

methyl 5-norbomen-2-carboxylate,

2-hydroxyethyl 5-norbornen-2-carboxylate,

5-norbomen-2-methanol,

5-norbomen-2, 3-dicarboxylic acid anhydride, and the like.

When U in —COOU is acid-labile group, the structural unit of the formula(c) is a structural unit having acid-labile group even if it hasnorbomene structure. Examples of monomers giving structural unit havingacid-labile group include t-butyl 5-norbornen-2-carboxylate,1-cyclohexyl-1-methylethyl 5-norbornen-2-carboxylate, 1-methylcyclohexyl5-norbornen-2-carboxylate, 2-methyl-2-adamantyl5-norbornen-2-carboxylate, 2-ethyl-2-adamantyl 5-norbomen-2-carboxylate,1-(4-methylcyclohexyl)-1-methylethyl 5-norbornen-2-carboxylate,1-(4-hydroxylcyclohexyl)-1-methylethyl 5-norbornen-2carboxylate,1-methyl-1-(4-oxocyclohexyl)ethyl 5-norbornen-2-carboxylate,1-(1-adamantyl)-1-methylethyl 5-norbornen-2-carboxylate, and the like.

The resin used in the present composition preferably contains structuralunit(s) having an acid-labile group generally in a ratio of 10 to 80% bymol in all structural units of the resin though the ratio variesdepending on the kind of radiation for patterning exposure, the kind ofan acid-labile group, and the like.

When the structural units particularly derived from 2-alkyl-2-adamantyl(meth)acrylate or 1-(1-adamantyl)-1-alkylalkyl (meth)acrylate are usedas the acid-labile group, it is advantageous in dry-etching resistanceof the resist that the ratio of the structural units is 15% by mol ormore in all structural units of the resin.

When, in addition to structural units having an acid-labile group, otherstructural units having acid-stable group are contained, it ispreferable that the sum of these structural units is in the range of 20to 90% by mol based on all structural units of the resin.

When alicyclic compound having olefinic double bond and aliphaticunsaturated dicarboxylic anhydride are used as copolymerization monomer,it is preferable to use them in excess amount in view of a tendency thatthese are not easily polymerized.

In the present composition, performance deterioration caused byinactivation of acid which occurs due to post exposure delay can bediminished by adding basic compounds, particularly, basicnitrogen-containing organic compounds, for example, amines as aquencher.

Specific examples of such basic nitrogen-containing organic compoundsinclude the ones represented by the following formulae:

In the formulas, T¹² and T¹³ each independently represent a hydrogenatom, an alkyl group, a cycloalkyl group or an aryl group. The alkylgroup preferably has bout 1 to 6 carbon atoms, the cycloalkyl grouppreferably has about 5 to 10 carbon atoms, and the aryl group preferablyhas about 6 to 10 carbon atoms. Furthermore, at least one hydrogen atomon the alkyl group, cycloalkyl group or aryl group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may each independently be substituted with alkyl grouphaving 1 to 4 carbon atoms.

T¹⁴, T¹⁵ and T¹⁶ each independently represent a hydrogen atom, an alkylgroup, a cycloalkyl group, an aryl group or an alkoxy group. The alkylgroup preferably has about 1 to 6 carbon atoms, the cycloalkyl grouppreferably has about 5 to 10 carbon atoms, the aryl group preferably hasabout 6 to 10 carbon atoms, and the alkoxy group preferably has about 1to 6 carbon atoms. Furthermore, at least one hydrogen atom on the alkylgroup, cycloalkyl group, aryl group or alkoxy group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may be substituted with alkyl group having 1 to 4 carbonatoms.

T¹⁷ represents an alkyl group or a cycloalkyl group. The alkyl grouppreferably has about 1 to 6 carbon atoms, and the cycloalkyl grouppreferably has about 5 to 10 carbon atoms. Furthermore, at least onehydrogen atom on the alkyl group or cycloalkyl group may eachindependently be substituted with hydroxyl group, amino group, or alkoxygroup having 1 to 6 carbon atoms. At least one hydrogen atom on theamino group may be substituted with alkyl group having 1 to 4 carbonatoms.

In the formulas, T¹⁸ represents an alkyl group, a cycloalkyl group or anaryl group. The alkyl group preferably has about 1 to 6 carbon atoms,the cycloalkyl group preferably has about 5 to 10 carbon atoms, and thearyl group preferably has about 6 to 10 carbon atoms. Furthermore, atleast one hydrogen atom on the alkyl group, cycloalkyl group or arylgroup may each independently be substituted with a hydroxyl group, anamino group, or an alkoxy group having 1 to 6 carbon atoms. At east onehydrogen atom on the amino group may each independently be substitutedwith alkyl group having 1 to 4 carbon atoms.

However, none of T¹² and T¹³ in the compound represented by the aboveformula [3] is a hydrogen atom.

A represents alkylene group, carbonyl group, imino group, sulfide groupor disulfide group. The alkylene group preferably has about 2 to 6carbon atoms.

Moreover, among T¹²-T¹⁸, in regard to those which can bestraight-chained or branched, either of these may be permitted.

T¹⁹, T²⁰ and T²¹ each independently represent a hydrogen atom, an alkylgroup having 1 to 6 carbon atoms, an aminoalkyl group having 1 to 6carbon atoms, a hydroxyalkyl group having 1 to 6 carbon atoms or asubstituted or unsubstituted aryl group having 6 to 20 carbon atoms, orT¹⁹ and T²⁰ bond to form an alkylene group which forms a lactam ringtogether with adjacent —CO—N—.

Examples of such compounds include hexylamine, heptylamine, octylamine,nonylamine, decylamine, aniline, 2-, 3- or 4-methylaniline,ethylenediamine, tetramethylenediamine, hexamethylenediamine,4,4′-diamino-1,2-diphenylethane,4,4′-diamino-3,3′-dimethyldiphenylmethane,4,4′-diamino-3,3′-diethyldiphenylmethane, dibutylamine, dipentylamine,dihexylamine, diheptylamine, dioctylamine, dinonylamine, didecylamine,N-methylaniline, piperidine, diphenylamine, triethylamine,trimethylamine, tripropylamine, tributylamine, tripentylamine,trihexylamine, triheptylamine, trioctylamine, trinonylamine,tridecylamine, methyldibutylamine, methyldipentylamine,methyldihexylamine, methyldicyclohexylamine, methyldiheptylamine,methyldioctylamine, methyldinonylamine, methyldidecylamine,ethyldibutylamine, ethydipentylamine, ethyldihexylamine,ethydiheptylamine, ethyldioctylamine, ethyldinonylamine,ethyldidecylamine, dicyclohexylmethylamine,tris[2-(2-methoxyethoxy)ethyl]amine, triisopropanolamine,N,N-dimethylaniline, 2,6-isopropylaniline, pyridine, 4-ethylpyridine,bipyridine, 2,2′-dipyridylamine, di-2-pyridyl ketone,1,2-di(2-pyridyl)ethane, 1,2-di(4-pyridyl)ethane,1,3-di(4-pyridyl)propane, 1,2-bis(2-pyridyl)ethylene,1,2-bis(4-pyridyl)ethylene, 4,4′-dipyridyl sulfide, 4,4′-dipyridyldisulfide, 1,2-bis(4-pyridyl)ethylene, 2,2′-dipicolylamine,3,3′-dipicolylamine, tetramethylammonium hydroxide,tetraisopropylammonium hydroxide, tetrabutylammonium hydroxide,tetra-n-hexylammonium hydroxide, tetra-n-octylammonium hydroxide,phenyltrimethylammonium hydroxide,3-trifluoromethylphenyltrimethylammonium hydroxide,(2-hydroxyethyl)trimethylammonium hydroxide (so-called “choline”),N-methylpyrrolidone, and the like.

Furthermore, hindered amine compounds having piperidine skeleton asdisclosed in JP-A-H11-52575 can be used as quencher.

It is preferable that the present composition contains resin componentin an amount of about 80 to 99.9% by weight and Salt (I) in an amount of0.1 to 20% by weight on the total amount of the resin component and Salt(I).

When basic compound is used as a quencher, the basic compound iscontained preferably in an amount of about 0.01 to 5 parts, morepreferably in an amount of about 0.01 to 1 part, by weight per 100 partsby weight of sum of resin component and Salt (I).

The present composition can contain, if necessary, various additives insmall amount such as a sensitizer, solution suppressing agent, otherpolymers, surfactant, stabilizer, dye and the like, as long as theeffect of the present invention is not prevented.

The present composition is usually in the form of a resist liquidcomposition in which the aforementioned ingredients are dissolved in asolvent, and the resist liquid composition is to be applied onto asubstrate such as a silicon wafer by a conventional process such as spincoating. The solvent used here is sufficient to dissolve theaforementioned ingredients, have an adequate drying rate, and give auniform and mooth coat after evaporation of the solvent and, hence,solvents generally used in the art can be used. In the presentinvention, the total solid content means total content exclusive ofsolvents.

Examples thereof include glycol ether esters such as ethyl Cellosolveacetate, methyl Cellosolve acetate and propylene glycol monomethyl etheracetate; glycol ethers such as propylene glycol monomethyl ether,di(ethylene glycol) dimethyl ether; esters such as ethyl lactate, butyllactate, amyl lactate and ethyl pyruvate and the like; ketones such asacetone, methyl isobutyl ketone, 2-heptanone and cyclohexanone; cyclicesters such as y-butyrolactone, and the like. These solvents can be usedeach alone or in combination of two or more.

A resist film applied onto the substrate and then dried is subjected toexposure for patterning, then heat-treated for facilitating a deblockingreaction, and thereafter developed with an alkali developer. The alkalideveloper used here may be any one of various alkaline aqueous solutionsused in the art, and generally, an aqueous solution oftetramethylammonium hydroxide or (2-hydroxyethyl)trimethylammoniumhydroxide (commonly known as “choline”) is often used.

It should be construed that embodiments disclosed here are examples inall aspects and not restrictive. It is intended that the scope of thepresent invention is determined not by the above descriptions but byappended Claims, and includes all variations of the equivalent meaningsand ranges to the Claims.

The present invention will be described more specifically by way ofexamples, which are not construed to limit the scope of the presentinvention. The “%” and “part(s)” used to represent the content of anycomponent and the amount of any material used in the following examplesand comparative examples are on a weight basis unless otherwisespecifically noted. The weight-average molecular weight of any materialused in the following examples is a value found by gel permeationchromatography [HLC-812OGPC Type, Column (Three Columns): TSKgelMultipore HXL-M, Solvent: Tetrahydrofuran, manufactured by TOSOHCORPORATION] using styrene as a standard reference material. Structuresof compounds were determined by NMR (GX-270 Type, or EX-270 Type,manufactured by JEOL LTD) and mass spectrometry (Liquid Chromatography:1100 Type, manufactured by Agilient, Mass Spectrometry: LC/MSD Type orLCD/MSD TOF Type, manufactured by Agilient).

EXAMPLE 1 (Synthesis of triphenylsulfonium(3-phenyl-1-propoxycarbonyl)difluoromethanesulfonate

-   (1) 230 Parts of 30% aqueous sodium hydroxide solution was added    dropwise into a mixture of 100 parts of methyl    difluoro(fluorosulfonyl)acetate and 250 parts of ion-exchanged water    in a ice bath. The added mixture was heated and refluxed at 100° C.    for 2.5 hours. After cooling, the cooled mixture was neutralized    with 88 parts of conc. hydrochloric acid and concentrated to obtain    158.4 parts of sodium difluorosulfoacetate (containing inorganic    salt, purity: 65.1%).-   (2) 5.0 Parts of sodium difluorosulfoacetate (purity: 65.1%), 4.48    parts of 3-phenyl-1-propanol and 100 parts of toluene were charged    in a vessel, 3.26 parts of p-toluenesulfonic acid (p-TsOH) was added    thereto, and the mixture was refluxed for 12 hours. After    concentrating the mixture to remove toluene, 67 parts of n-heptane    was added thereto and the added mixture was stirred to wash, and the    solid was obtained by filtration. The solid obtained by filtration    was added with 44 parts of ethyl acetate and the mixture was stirred    and filtrated. The filtrate was concentrated to obtain 3.81 parts of    sodium salt of 3-phenyl-1-propyl difluorosulfoacetate.

H-NMR data (dimethylsulfoxide-d₆, Internal Standard: tetramethylsilane):d(ppm) 1.85-1.96 (m, 2H); 2.67 (t, 2H, J=7.9 Hz); 4.20 (t, 2H, J=6.3Hz); 7.15-7.31 (m, 5H)

-   (3) 3.61 Parts of sodium salt of 3-phenyl-1-propyl    difluorosulfoacetate obtained in (2) above was dissolved in 18 parts    of ion-exchanged water and 18 parts of acetonitrile. To the    solution, a solution of 3.58 parts of triphenylsulfonium chloride,    18 parts of ion-exchanged water and 18 parts of acetonitrile was    added. The added mixture was stirred over night. After the stirring,    the resulting mixture was concentrated, and then the concentrate was    extracted with 102 parts of chloroform. The organic layer was washed    with ion-exchanged water. The washed organic layer was concentrated.    The concentrate was washed with 64 parts of tert-butyl methyl ether    and the upper layer, washed solvent, was decanted and removed. The    residual lower layer was concentrated to obtain 5.68 parts of    triphenylsulfonium    (3-phenyl-1-propoxycarbonyl)difluoromethanesulfonate in the form of    orange oil, which is called as acid generator B1.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 1.85-1.95 (m, 2H); 2.67 (t, 2H, J=8.1 Hz);4.19 (t, 2H, J=6.5 Hz); 7.14-7.30 (m, 5H); 7.75-7.90 (m, 15H)

MS (ESI (+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS (ESI (−) Spectrum): M−293.0 (C₁₁H₁₁F₂O₅S⁻=293.03)

EXAMPLE 2 (Synthesis of triphenylsulfonium(2-phenylethoxycarbonyl)difluoromethanesulfonate)

-   (4) 5.0 Parts of sodium difluorosulfoacetate (purity: 65.1%), 4.01    parts of 2-phenylethanol and 100 parts of toluene were charged in a    vessel, 3.26 parts of p-toluenesulfonic acid (p-TsOH) was added    thereto, and the mixture was refluxed for 6 hours. After    concentrating the mixture to remove toluene, 73 parts of n-heptane    was added thereto and the added mixture was stirred to wash, and the    solid was obtained by filtration. The solid obtained by filtration    was added with 50 parts of ethyl acetate and the mixture was stirred    and filtrated. The filtrate was concentrated to obtain 3.60 parts of    sodium salt of 2-phenylethyl difluorosulfoacetate.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 2.93 (t, 2H, J=6.9 Hz); 4.40 (t, 2H, J=6.9Hz); 7.19-7.34 (m, 5H)

-   (5) 3.36 Parts of sodium salt of 2-phenylethyl difluorosulfoacetate    obtained in (4) above was dissolved in 17 parts of ion-exchanged    water and 17 parts of acetonitrile. To the solution, a solution of    3.49 parts of triphenylsulfonium chloride, 17 parts of ion-exchanged    water and 17 parts of acetonitrile was added. The added mixture was    stirred over night. After the stirring, the resulting mixture was    concentrated, and then the concentrate was extracted with 91 parts    of chloroform. The organic layer was washed with ion-exchanged    water. The washed organic layer was concentrated. The concentrate    was washed with 54 parts of tert-butyl methyl ether and the upper    layer, washed solvent, was decanted and removed. The residual lower    layer was concentrated to obtain 4.90 parts of triphenylsulfonium    (2-phenylethoxycarbonyl)difluoromethanesulfonate in the form of    orange oil, which is called as acid generator B2.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 2.93 (t, 2H, J=7.1 Hz); 4.39 (t, 2H, J=6.9Hz); 7.19-7.33 (m, 5H); 7.75-7.90 (m, 15H)

MS (ESI (+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS (ESI (−) Spectrum): M−279.0 (C₁₀H₉F₂O₅O₅S⁻=279.01)

EXAMPLE 3 (Synthesis of triphenylsulfonium(2-(naphthalen-1-yl)ethoxycarbonyl)difluoromethanesulfonate

-   (6) 4.0 Parts of sodium difluorosulfoacetate (purity: 65.1%), 4.53    parts of 2-naphthalenethanol and 100 parts of toluene were charged    in a vessel, 2.60 parts of p-toluenesulfonic acid (p-TsOH) was added    thereto, and the mixture was refluxed for 24 hours. After    concentrating the mixture to remove toluene, 60 parts of tert-butyl    methyl ether was added thereto and the added mixture was stirred to    wash, and the solid was obtained by filtration. The solid obtained    by filtration was added with 43 parts of ethyl acetate and the    mixture was stirred and filtrated. The filtrate was concentrated to    obtain 2.12 parts of sodium salt of 2-(naphthalen-1-yl)ethyl    difluorosulfoacetate.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 3.42 (t, 2H, J=7.1 Hz); 4.52 (t, 2H, J=7.1Hz); 7.42-7.61 (m, 4H); 7.81-7.84 (m, 1H); 7.91 (d, 1H, J=9.1 Hz); 8.14(d, 1H, J=7.9 Hz)

-   (7) 2.04 Parts of sodium salt of 2-(naphthalen-1-yl)ethyl    difluorosulfoacetate obtained in (6) above was dissolved in 10 parts    of ion-exchanged water and 10 parts of acetonitrile. To the    solution, a solution of 1.82 parts of triphenylsulfonium chloride, 9    parts of ion-exchanged water and 9 parts of acetonitrile was added.    The added mixture was stirred over night. After the stirring, the    resulting mixture was concentrated, and then the concentrate was    extracted with 91 parts of chloroform. The organic layer was washed    with ion-exchanged water. The washed organic layer was concentrated.    The concentrate was washed with 35 parts of tert-butyl methyl ether    and the upper layer, washed solvent, was decanted and removed. The    residual lower layer was concentrated to obtain 2.97 parts of    triphenylsulfonium (2-phenylethoxycarbonyl)difluoromethanesulfonate    in the form of orange oil, which is called as acid generator B3.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 3.41 (t, 2H, J=7.3 Hz); 4.51 (t, 2H, J=7.3Hz); 7.41-7.61 (m, 4H); 7.75-7.96 (m, 17H); 8.13 (d, 1H, J=7.9 Hz)

MS (ESI (+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS (ESI (−) Spectrum): M−329.0 (C₁₄H₁₁F₂O₅S⁻=329.03)

EXAMPLE 4 (Synthesis of triphenylsulfonium(9H-fluoren-9-yl)methoxycarbonyl)difluoromethanesulfonate

-   (8) 3.5 Parts of sodium difluorosulfoacetate (purity: 65.1%), 4.51    parts of 9-fluorenemethol and 70 parts of dichloroethane were    charged in a vessel, 2.28 parts of p-toluenesulfonic acid (p-TsOH)    was added thereto, and the mixture was refluxed for 4.5 hours, 70    parts of toluene was further added thereto and the added mixture was    refluxed for 22 hours. After concentrating the mixture to remove    dichloromethane and toluene, 48 parts of tert-butyl methyl ether was    added thereto and the added mixture was stirred to wash, and the    solid was obtained by filtration. The solid obtained by filtration    was added with 43 parts of ethyl acetate and the mixture was stirred    and filtrated. The filtrate was concentrated to obtain 2.04 parts of    sodium salt of (9H-fluoren-9-yl)methyl difluorosulfoacetate.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 4.29 (t, 1H, J=7.6 Hz); 4.46 (s, 1H); 4.48(s, 1H); 7.33 (t, 2H, J=7.3 Hz); 7.44 (t, 2H, J=7.6 Hz); 7.82 (d, 2H,J=7.3 Hz); 7.90 (d, 2H, J=7.3 Hz)

-   (9) 2.01 Parts of sodium salt of (9H-fluoren-9-yl)methyl    difluorosulfoacetate obtained in (8) above was dissolved in 10 parts    of ion-exchanged water and 10 parts of acetonitrile. To the    solution, a solution of 1.68 parts of triphenylsulfonium chloride, 8    parts of ion-exchanged water and 8 parts of acetonitrile was added.    The added mixture was stirred over night. After the stirring, the    resulting mixture was concentrated, and then the concentrate was    extracted with 54 parts of chloroform. The organic layer was washed    with ion-exchanged water. The washed organic layer was concentrated.    The concentrate was washed with 37 parts of tert-butyl methyl ether    and the upper layer, washed solvent, was decanted and removed. The    residual lower layer was concentrated to obtain 2.78 parts of    triphenylsulfonium    (9H-fluoren-9-yl)methoxycarbonyl)difluoromethanesulfonate in the    form of orange oil, which is called as acid generator B4.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 4.29 (t, 1H, J=7.8 Hz); 4.45 (s, 1H); 4.48(s, 1H); 7.32 (t, 2H, J=7.4 Hz); 7.43 (t, 2H, J=7.4 Hz); 7.75-7.92 (m,19H)

MS (ESI (+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS (ESI (−) Spectrum): M−353.0 (C₁₆H₁₁F₂O₅S⁻=353.03)

EXAMPLE 5 (Synthesis of triphenylsulfonium(1-(5-hydroxynaphthyl)oxyethoxycarbonyl)difluoromethanesulfonate

-   (10) 25 Parts of 1,5-dihydroxynaphthalene and 250 parts of    ion-exchanged water were charged in a vessel, a solution of 12.5    parts of sodium hydroxide and 125parts of ion-exchanged water was    added thereto and the mixture was stirred for 30 minutes. After    stirring, 25.4 parts of 2-bromoethanol was added dropwise for 1    hour, and the added mixture was stirred for 15 hours. After    stirring, the stirred mixture was added with conc. hydrochloric acid    to become its pH to 1. 250 parts of ethyl acetate was added thereto    to extract. The mixture was phase-separated and the organic layer    was washed with ion-exchanged water. The washed organic layer was    concentrated and the concentrate was purified by silica gel column    chromatography to obtain 14.5 parts of    5-(2-hydroxyethoxy)naphthalene-1-ol.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 3.85 (q, 2H); 4.13 (t, 2H); 4.95 (t, 1H);6.90 (t, 2H); 7.29 (dt, 2H); 7.69 (d, 2H); 10.00(s, 1H)

-   (11) 1145 Parts of 30% aqueous sodium hydroxide solution was added    dropwise into a mixture of 500 parts of methyl    difluoro(fluorosulfonyl)acetate and 750 parts of ion-exchanged water    in a ice bath. The added mixture was heated and refluxed at 100° C.    for 2.5 hours. After cooling, the cooled mixture was neutralized    with 88 parts of conc. hydrochloric acid and concentrated to obtain    802.8 parts of sodium difluorosulfoacetate (containing inorganic    salt, purity: 64.2%).-   (12) 20.0 Parts of sodium difluorosulfoacetate (purity: 64.2%)    obtained in (2) above, 6.62 parts of    5-(2-hydroxyethoxy)naphthalene-1-ol and 190 parts of dichloroethane    were charged in a vessel, 12.33 parts of p-toluenesulfonic acid    (p-TsOH) was added thereto, and the mixture was refluxed for 12    hours. After concentrating the mixture to remove dichloromethane,    200 parts of acetonitrile was added thereto and the added mixture    was stirred and filtrated twice. The filtrate was concentrated and    the concentrate was purified by silica gel column chromatography to    obtain 4.50 parts of sodium salt of 1-(5-hydroxynaphthyl)oxyethyl    difluorosulfoacetate.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 4.37 (t, 2H); 4.70 (t, 2H); 6.89 (d, 1H);6.96 (d, 1H); 7.30 (dt, 2H); 7.59 (d, 1H); 7.72 (d, 1H)

-   (13) 4.50 Parts of sodium salt of 1-(5-hydroxynaphthyl)oxyethyl    difluorosulfoacetate obtained in (12) above was dissolved in 45    parts of acetonitrile. To the solution, a solution of 3.50 parts of    triphenylsulfonium chloride and 35.0 parts of ion-exchanged water    was added. The added mixture was stirred for 15 hours. After the    stirring, the resulting mixture was concentrated, and then the    concentrate was extracted with 100 parts of chloroform. The organic    layer was washed with ion-exchanged water. The washed organic layer    was concentrated. The concentrate was washed with 5 parts of    acetonitrile and 100 parts of ion-exchanged water, then washed with    100 parts of acetonitrile and the solid was filtered to obtain 1.72    parts of triphenylsulfonium (1-(5-hydroxynaphthyl)oxyethoxycarbonyl)    difluoromethanesulfonate in the form of white solid, which is called    as acid generator B5.

¹H-NMR data (dimethylsulfoxide-d₆, Internal Standard:tetramethylsilane): d(ppm) 4.36 (t, 2H); 4.69 (t, 2H); 6.88 (d, 1H);6.96 (d, 1H); 7.29 (dt, 2H); 7.58 (d, 1H); 7.71 (d, 1H); 7.75-7.90 (m,15H); 10.04 (s, 1H)

MS (ESI (+) Spectrum): M+263.0 (C₁₈H₁₅S⁺=263.09)

MS (ESI (−) Spectrum): M−361.0 (C₁₄H₁₁F₂O₇S⁻=361.02)

Resin Synthesis Example 1 (Synthesis of Resin A1)

2-Ethyl-2-adamantyl methacrylate, 3-hydroxy-1-adamantyl methacrylate andα-methacryloyloxy-γ-butyrolactone were charged at a molar ratio of5:2.5:2.5 (20.0 parts:9.5 parts:7.3 parts), and methyl isobutyl ketonein twice weight based on all monomers was added, to prepare solution. Tothe solution was added azobisisobutyronitrile as an initiator in a ratioof 2 mol % based on all monomer molar amount, and the mixture was heatedat 80° C. for about 8 hours. Then, the reaction solution was poured intolarge amount of heptane to cause precipitation, and this operation wasrepeated three times for purification. As a result, copolymer having aweight-average molecular weight of about 9200 was obtained. This iscalled resin A1.

Examples 1 to 5 and Comparative Example 1

The following components were mixed and dissolved, further, filtratedthrough a fluorine resin filter having pore diameter of 0.2 μm, toprepare resist liquid.

-   <Resin>-   resin A1: 10 parts-   <Acid generator>    -   Acid generator B1: 0.241 part    -   Acid generator B2: 0.235 part    -   Acid generator B3: 0.257 part    -   Acid generator B4: 0.267 part    -   Acid generator B5: 0.270 part    -   Acid generator C1    -   triphenylsulfonium perfluorobutanesulfonate: 0.244 part-   <Quencher>-   quencher Q1: 2,6-diisopropylaniline 0.0325 part

<Solvent> Solvent Y1: propylene glycol monomethyl ether acetate 80.0parts propylene glycol monomethyl ether 20.0 parts γ-butyrolactone 3.0parts

Silicon wafers were each coated with “ARC-29A-8”, which is an organicanti-reflective coating composition available from Brewer Co., and thenbaked under the conditions: 205° C., 60 seconds, to form a 780 Å-thickorganic anti-reflective coating. Each of the resist liquids prepared asabove was spin-coated over the anti-reflective coating so that thethickness of the resulting film became 0.25 μm after drying. The siliconwafers thus coated with the respective resist liquids were each prebakedon a direct hotplate at a temperature of 130° C. for 60 seconds. Usingan ArF excimer stepper (“NSR ArF” manufactured by Nikon Corporation,NA=0.55, 2/3 Annular), each wafer thus formed with the respective resistfilm was subjected to line and space pattern exposure, with the exposurequantity being varied stepwise.

After the exposure, each wafer was subjected to post-exposure baking ona hotplate at a temperature of 130° C. for 60 seconds and then to paddledevelopment for 60 seconds with an aqueous solution of 2.38wt %tetramethylammonium hydroxide.

A bright field pattern developed on the organic anti-reflective coatingsubstrate was observed with a scanning electron microscope, the resultsof which are shown in Table 1. The term “bright field pattern”, as usedherein, means a pattern obtained by exposure and development through areticle comprising an outer frame made of a glass layer(light-transmitting layer) and linear chromium layers (light-shieldinglayers) formed on a glass surface (light-transmitting portion) extendinginside the outer frame. Thus, the bright field pattern is such that,after exposure and development, resist layer surrounding the line andspace pattern is removed.

Effective Sensitivity (ES):

It is expressed as the amount of exposure that the line pattern(light-shielding layer) and the space pattern (light-transmitting layer)become 1:1 after exposure through 0.13 μm line and space pattern maskand development.

Resolution:

It is expressed as the minimum size of space pattern which gave thespace pattern split by the line pattern at the exposure amount of theeffective sensitivity. TABLE 1 Acid Resolution No. Generator (μm) ES(mJ/cm²) Example 1 B1 0.12 20.0 Example 2 B2 0.12 20.0 Example 3 B3 0.1227.5 Example 4 B4 0.12 27.5 Example 5 B5 0.12 32.5 Comparative C1 0.1322.5 Example 1

Salt (I) is suitably used for an acid generator capable of providingchemically amplified resist compositions giving patterns havingexcellent resolution, and the present resist composition is especiallysuitably used for chemically amplified resist compositions for ArFexcimer laser lithography, KrF excimer laser lithography and ArFimmersion lithography.

1. A salt of the formula (I):

wherein X represents alkylene group or substituted alkylene group inwhich a —CH₂— except for the one connected to the adjacent —COO— issubstituted with —S— or —O—; Y represents hydrocarbon ring groupcontaining at least one aromatic ring and having 5 to 30 carbon atoms inwhich one or more of —CH₂— on the hydrocarbon ring is optionallysubstituted with —O— or —CO— and in which one or more of hydrogen atomon the hydrocarbon ring is optionally substituted with alkyl grouphaving 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ and Q²each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; A⁺ represents organic counter ion; and nshows 0 or
 1. 2. The salt according to claim 1, wherein each of Q¹ andQ² is fluorine atom or trifluoromethyl group.
 3. The salt according toclaim 1, wherein n is 1 and X is alkylene group having 1 to 6 carbonatoms or substituted alkylene group having 1 to 6 carbon atoms in whicha —CH₂— except for the one connected to the adjacent —COO— issubstituted with —S— or —O—.
 4. The salt according to claim 1, wherein nis
 0. 5. The salt according to claim 3, wherein X is —CH₂—, —CH₂CH₂—,—CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂— or —CH₂CH₂—O—.
 6. The salt according toclaim 1, wherein Y is aromatic ring group having 5 to 20 carbon atoms inwhich one or more of hydrogen atom in the aromatic ring is optionallysubstituted with alkyl group having 1 to 6 carbon atoms, alkoxy grouphaving 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbonatoms, hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group orcyano group.
 7. The salt according to claim 1, wherein Y is phenylgroup, naphthyl group, anthryl group, phenanthryl group or fluorenylgroup in which one or more of hydrogen atom on the ring is optionallysubstituted with alkyl group having 1 to 6 carbon atoms, alkoxy grouphaving 1 to 6 carbon atoms, perfluoroalkyl group having 1 to 4 carbonatoms, hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group orcyano group.
 8. The salt according to claim 1, wherein A⁺ is at leastone cation selected from the group consisting of the formula (IIe), theformula (IIb), the formula (IIc) and the formula (IId): a cation of theformula (IIe);

 wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl grouphaving 1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30carbon atoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation ofthe formula (IIb);

 wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms; a cation of the formula (IIc);

 wherein P⁶ and P⁷ each independently represent alkyl having 1 to 12carbon atoms or cycloalkyl having 3 to 12 carbon atoms, or P⁶ and P⁷bond to form divalent acyclic hydrocarbon group having 3 to 12 carbonatoms which forms a ring together with the adjacent S⁺, and at least one—CH₂— in the divalent acyclic hydrocarbon group is optionallysubstituted by —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl having 1 to 12 carbon atoms, cycloalkyl having 3 to 12 carbonatoms or aromatic ring group optionally substituted, or P⁸ and P⁹ bondto form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyltogether with the adjacent —CHCO—, and at least one —CH₂— in thedivalent acyclic hydrocarbon group is optionally substituted by —CO—,—O— or —S—; and a cation of the formula (IId);

 wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹each independently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms,B represents sulfur atom or oxygen atom, and m represents 0 or
 1. 9. Thesalt according to claim 8, wherein the cation of the formula (IIe) is acation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms; and P³¹, P³²P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydroxyl group, alkylgroup having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbonatoms or cyclic hydrocarbon group having 3 to 12 carbon atoms, and l, k,j, i, h and g each independently show an integer of 0 to
 5. 10. The saltaccording to claim 8, wherein the cation of the formula (IIe) is acation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.
 11. The salt according to claim 10, whereinthe cation of the formula (IIa) is a cation of the formula (IIi):

wherein P²², P²³ and P²⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 atoms.
 12. The salt according to claim 1,wherein the salt is that of the formula (IIIa), (IIIb), (IIIc), (IIId)or (IIIe):

wherein n1 shows an integer of 0 to 6, n2 shows an integer of 1 to 6,and P²², P²³ and P²⁴ have the same meanings as defined above.
 13. A saltof the formula (IV):

wherein X represents alkylene group or substituted alkylene group inwhich a —CH₂— except for the one connected to the adjacent —COO— issubstituted with —S— or —O—; Y represents hydrocarbon ring groupcontaining at least one aromatic ring and having 5 to 30 carbon atoms inwhich one or more of —CH₂— on the hydrocarbon ring is optionallysubstituted with —O— or —CO— and in which one or more of hydrogen atomon the hydrocarbon ring is optionally substituted with alkyl grouphaving 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ and Q²each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; M represents Li, Na, K or Ag; and n shows 0or
 1. 14. A process for producing a salt of the formula (IV):

wherein X represents alkylene group or substituted alkylene group inwhich a —CH₂— except for the one connected to the adjacent —COO— issubstituted with —S— or —O—; Y represents hydrocarbon ring groupcontaining at least one aromatic ring and having 5 to 30 carbon atoms inwhich one or more of —CH₂— on the hydrocarbon ring is optionallysubstituted with —O— or —CO— and in which one or more of hydrogen atomon the hydrocarbon ring is optionally substituted with alkyl grouphaving 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ and Q²each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; M represents Li, Na, K or Ag; and n shows 0or 1, which comprises esterifying an alcohol of the formula (V):HO—(X)_(n)—Y  (V)  wherein X, Y and n have the same meanings as definedabove, with a carboxylic acid of the formula (VI):

 wherein M and Q have the same meanings as defined above.
 15. A processfor producing a salt of the formula (I):

wherein X represents alkylene group or substituted alkylene group inwhich a —CH₂— except for the one connected to the adjacent —COO— issubstituted with —S— or —O—; Y represents hydrocarbon ring groupcontaining at least one aromatic ring and having 5 to 30 carbon atoms inwhich one or more of —CH₂— on the hydrocarbon ring is optionallysubstituted with —O— or —CO— and in which one or more of hydrogen atomon the hydrocarbon ring is optionally substituted with alkyl grouphaving 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ and Q²each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; A⁺ represents organic counter ion; and nshows 0 or 1, which comprises reacting a salt of the formula (IV):

 wherein M represents Li, Na, K or Ag, and X, Y, Q¹, Q² and n have thesame meanings as defined above, with a compound of the formula (VII):A⁺Z⁻  (VII)  wherein Z represents F, Cl, Br, I, BF₄, AsF₆, SbF₆, PF₆ orClO₄, and A⁺ has the same meaning as defined above.
 16. A chemicallyamplified resist composition comprising a salt of the formula (I):

 wherein X represents alkylene group or substituted alkylene group inwhich a —CH₂— except for the one connected to the adjacent —COO— issubstituted with —S— or —O—; Y represents hydrocarbon ring groupcontaining at least one aromatic ring and having 5 to 30 carbon atoms inwhich one or more of —CH₂— on the hydrocarbon ring is optionallysubstituted with —O— or —CO— and in which one or more of hydrogen atomon the hydrocarbon ring is optionally substituted with alkyl grouphaving 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group; Q¹ and Q²each independently represent fluorine atom or perfluoroalkyl grouphaving 1 to 6 carbon atoms; A⁺ represents organic counter ion; and nshows 0 or 1, and a resin which contains a structural unit having anacid-labile group and which itself is insoluble or poorly soluble in analkali aqueous solution but becomes soluble in an alkali aqueoussolution by the action of an acid.
 17. The composition according toclaim 16, wherein each of Q¹ and Q² is fluorine atom or trifluoromethylgroup.
 18. The composition according to claim 16, wherein the resincontains a structural unit derived from a monomer having a bulky andacid-labile group.
 19. The composition according to claim 18, whereinthe bulky and acid-labile group is 2-alkyl-2-adamantyl group or1-(1-adamantyl)-1-alkylalkyl group.
 20. The composition according toclaim 18, wherein the monomer having bulky and acid-labile group is2-alkyl-2-adamantyl (meth)acrylate, 1-(1-adamantyl)-1-alkylalkyl(meth)acrylate, 2-alkyl-2-adamantyl 5-norbornene-2-carboxylate,1-(1-adamantyl)-1-alkylalkyl 5-norbornene-2-carboxylate,2-alkyl-2-adamantyl α-chloroacrylate or 1-(1-adamantyl)-1-alkylalkylα-chloroacrylate.
 21. The composition according to claim 16, wherein thecomposition further comprises a basic compound.
 22. The compositionaccording to claim 16, wherein n is 1 and X is alkylene group having 1to 6 carbon atoms or substituted alkylene group having 1 to 6 carbonatoms in which a —CH₂— except for the one connected to the adjacent—COO— is substituted with —S— or —O.
 23. The composition according toclaim 16, wherein n is
 0. 24. The composition according to claim 16,wherein X is —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂CH₂CH₂CH₂— or —CH₂CH₂—O—.25. The composition according to claim 16, wherein Y is aromatic ringgroup having 5 to 20 carbon atoms in which one or more of hydrogen atomon the aromatic ring is optionally substituted with alkyl group having 1to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms,perfluoroalkyl group having 1 to 4 carbon atoms, hydroxyalkyl grouphaving 1 to 6 carbon atoms, hydroxyl group or cyano group.
 26. Thecomposition according to claim 16, wherein Y is phenyl group, naphthylgroup, anthryl group, phenanthryl group or fluorenyl group in which oneor more of hydrogen atom on the ring is optionally substituted withalkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6carbon atoms, perfluoroalkyl group having 1 to 4 carbon atoms,hydroxyalkyl group having 1 to 6 carbon atoms, hydroxyl group or cyanogroup.
 27. The composition according to claim 16, wherein A⁺ is at leastone cation selected from the group consisting of the formula (IIe), theformula (IIb), the formula (IIc) and the formula (IId): a cation of theformula (IIe);

 wherein P²⁵, P²⁶ and P²⁷ each independently represent alkyl grouphaving 1 to 30 carbon atoms or cyclic hydrocarbon group having 3 to 30carbon atoms, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms, a cation ofthe formula (IIb);

 wherein P⁴ and P⁵ each independently represent hydrogen atom, hydroxylgroup, alkyl group having 1 to 12 carbon atoms or alkoxy group having 1to 12 carbon atoms; a cation of the formula (IIc);

 wherein P⁶ and P⁷ each independently represent alkyl having 1 to 12carbon atoms or cycloalkyl having 3 to 12 carbon atoms, or P⁶ and P⁷bond to form divalent acyclic hydrocarbon group having 3 to 12 carbonatoms which forms a ring together with the adjacent S⁺, and at least one—CH₂— in the divalent acyclic hydrocarbon group is optionallysubstituted by —CO—, —O— or —S—, P⁸ represents hydrogen, P⁹ representsalkyl having 1 to 12 carbon atoms, cycloalkyl having 3 to 12 carbonatoms or aromatic ring group optionally substituted, or P⁸ and P⁹ bondto form divalent acyclic hydrocarbon group which forms 2-oxocycloalkyltogether with the adjacent —CHCO—, and at least one —CH₂— in thedivalent acyclic hydrocarbon group is optionally substituted by —CO—,—O— or —S—; and a cation of the formula (IId);

 wherein P¹⁰, P¹¹, P¹², P¹³, P¹⁴, P¹⁵, P¹⁶, P¹⁷, P¹⁸, P¹⁹, P²⁰ and P²¹each independently represent hydrogen atom, hydroxyl group, alkyl grouphaving 1 to 12 carbon atoms or alkoxy group having 1 to 12 carbon atoms,B represents sulfur atom or oxygen atom, and m represents 0 or
 1. 28.The composition according to claim 27, wherein the cation of the formula(IIe) is a cation of the formula (IIf), (IIg) or (IIh):

wherein P²⁸, P²⁹ and P³⁰ each independently represent alkyl group having1 to 20 carbon atoms or cyclic hydrocarbon group having 3 to 30 exceptphenyl group, wherein one or more hydrogen atom in the alkyl group isoptionally substituted with hydroxyl group, alkoxy group having 1 to 12carbon atoms or cyclic hydrocarbon group having 3 to 12 carbon atoms andwherein one or more hydrogen atom in the cyclic hydrocarbon group isoptionally substituted with hydroxyl group, alkyl group having 1 to 12carbon atoms or alkoxy group having 1 to 12 carbon atoms; and P³¹, P³²P³³, P³⁴, P³⁵ and P³⁶ each independently represent hydroxyl group, alkylgroup having 1 to 12 carbon atoms, alkoxy group having 1 to 12 carbonatoms or cyclic hydrocarbon group having 3 to 12 carbon atoms, and l, k,j, i, h and g each independently show an integer of 0 to
 5. 29. Thecomposition according to claim 27, wherein the cation of the formula(IIe) is a cation of the formula (IIa):

wherein P¹, P² and P³ each independently represent hydrogen atom,hydroxyl group, alkyl group having 1 to 12 carbon atoms or alkoxy grouphaving 1 to 12 carbon atoms.
 30. The composition according to claim 29,wherein the cation of the formula (IIa) is a cation of the formula(IIi):

wherein P²², P²³ and P²⁴ each independently represent hydrogen atom oralkyl group having 1 to 4 atoms.
 31. The composition according to claim30, wherein the salt is that of the formula (IIIa), (IIIb), (IIIc),(IIId) or (IIIe):

wherein n1 shows an integer of 0 to 6, n2 shows an integer of 1 to 6,and P²², P²³ and P²⁴ have the same meanings as defined above.